Liquid level and pressure control



' 30, 1940 s, R E 2,198,711

LIQUID LEVEL AND PRESSURE CONTROL Original Filed Aug. 5, 1937 2 Sheets-Sheet l as as 1N VENTOR.

ATTORNEY.

April 30, 1940. H. s. TURNER LIQUID LEVEL AND YRESSURE CONTROL Original Filed Aug. 5, 1937 2 Shaets-Sheet 2 X AMv n h n 41 XXX Q WW Y/ X VZV V/K/V K,

W 60 INVENTOR. BY

ATTORNEY.

Patented Apr. 30, 1940 PATENT. OFFICE 2,198,711 Lrqnin LEVEL AND PRESSURE CONTROL Hubert S. Turner, Brooklyn, N. Y. qRefiled for abandoned application Serial No;

'157,547, August 5,

1937. This application September 10, 1938, Serial No. 229,393

" 22 Claims. I

The control device of the present invention is anim'provement on and modification of the one disclosed in my co-pending application, Serial No. 86,999, filed June.24, 1936. This application 5 is refiled 'for the abandoned application filed August- 5, 1937, Serial No. 157,54

Heretofore ithas been customary to regulate the fuel combustion in a steam boiler by means -of a device operated by the steam pressure developed in the boiler; the combustion being diminished or completely, out off, whenever the steam pressure in the boiler has reached a'predetermined point.

Experience has shown that such a steam pressure, control, for a heating boiler, is'faulty in many respects and especially when used with a singlepipe steam heating system, which vents the air within the system by means of air valves located on the steam radiators and pipes. In 20 the case of the latter system, a comparatively high steam pressure is required to force the air out of the heating system through the air valves, within a reasonable time; though a comparatively low steam pressure is all that is required 25 to mainta'in the same, system steam saturated,

once the air hasbeen expelled.

Qnthisaccount, the combustion regulators heretofore used, are usually; set at a steam pressure that will expel the air and insure steam 30" saturation within the desired time interval. Ob

viously this is an uneconomical method of heating, inasmuch as the high air expelling steamv 35 to maintain, any steam pressure above the satura tio'n' point of the heating system, is out of all proportion to the slight'increase in heating effect of the higher pressure steam. I r m In the present invention means are provided 4 automatically 7 to provide exactly the correct steam pressure to remove the air from any given system, in any required time, and then check the consumption of fuel to the minimum needed to maintain "the entire heating system barely steam saturated and free from air, irrespective of what the actual steam pressure may be. Ex-- p'erience has shown that as long as the pressure within the heating system, aftersteam saturation'is obt'ained, is but slightly above atmospheric,

50 thereby preventing the inflow of air through the air valves, the greatest economy of fuel is obtained. l I

Taking advantage of the principles involved, I have been able to utilize my steam saturation 55" control for also functioning-as a high water cutoff, as a low water cut-off, as a steam pressure gauge and as a water level gauge, without any additions thereto.

In the drawings herewith, which are a part hereof:

Figure -1 represents a perspective view of one formof the invention;

Figure 2 represents diagrammatically a crosssection of a building with the device controlling the boiler, and t Figure 3 is an enlarged fragmentary view on the line 3-3 of Fig. 1.

Referring to Fig. 1, a base I is provided, which may be as shown or of any other desired form. Bracket 2 is rigidly fastened to base I by screws 3 and .4, which pass through slot 5 in bracket 2. A cradle 6 is pivoted at I and 8 in the two arms of bracket 2 and turns freely on these pivots. Rigidly supported on cradle 6, by clamp 9, is a hollow' pipe I0 which terminates in fittings II and I2. A counterweight I3 is adapted to slide along pipe l0 and is fastened thereto by a set screw. l 1

The lower and open end of a hollow glass vessel I4 is sealed'in fitting H. Similarly sealed in fitting I2, is a glass tube I5 which is also sealed in fitting l6 at its upper end. Connected to fitting l I is a plugged T I! and fastened in the side outlet thereof is a fiexible hose l8, which may be of metal, rubber or other suitable material. The pipe l0 establishes communication between the vessel l4 and tube l5 through the fittings I l and I2. Hose 18 is preferably formed in a loop, as shown, in order to obtain greater flexibility and is connected by pipe l9 (Figure 2) below the. low water level of boiler 20. Similarly connected to fitting I6 is flexible hose 2|, which is preferably looped, as shown in order to obtain greater flexibility and is connected by pipe 22 (Figure 2) above the normal water line of boiler 20. N

Fastened to a. lug of bracket 2 is insulating block 23, which supports electric contact springs 24 and25, to which are fastened at their free ends electric contacts 26 and 21. Fastened to an upward extending projection 28 at the rear of cradle 6, is adjusting screw bracket 29, which supports adjusting screws 30 and 3|. Held within this bracket by pivot 32 is circuit opener 33, which moves freely on its pivot. An insulating block '35. is fastened to 33 and engages the free ends of: springs 24 and 25. Circuit opener 33 has, two adjustable prongs 36 and 31 which pass over pin 38 attached to trip 39. Pivot 40 supports trip 39 and the latter turns freely thereon. Resting on the top of trip 39 is mercury switch holder 4| which clasps mercury switch 42. Pivot 43 supports holder 4| and the latter turns freely thereon. An extension 44 of holder 4| terminates in resetting button 45.

One end of heating coil 46 is fastened to bimetallic strip 41, which is fastened to bracket 48, mounted on insulating block 49. Wire 50 connects the coil electrically to spring 24. The other end of heating coil 46 is connected electrically to spring 25 by wire 5|. An adjustable electrical contact 52 is adapted to engage a contact on the free end of strip 41, when the latter is warped upward by heat from heating coil 46.

A purely conventional operative means is shown electrically connected to the device, which can be made to control any other form of operative means desired. Transformer 53 has its left secondary terminal connected by wire 54 to the lower terminal of solenoid 55 and its right secondary terminal connected by wire 56 to bracket 48. The upper terminal of solenoid 55 is connected by wire 51 to terminal 58.

The upper part of the plunger of solenoid 55 is encircled by the coiled spring 59 and is fastened by a pivot connection to the front part of holder 4|, so that this end is held higher than the back end which rests on trip 39 and consequently the mercury in switch 42 is'normally kept away from its contacts.

Wire 60 connects terminal 6| to terminal 62. Wire 63 connects terminal 64 to one terminal of the primary of transformer 53 and the other terminal is connected by wire 65 to terminal 6|. Wire 66 connects terminal 64 to one terminal of mercury switch 42, the other terminal being connected by wire 61 to terminal 68. Wire 69 connects wire 54 to terminal 18; wire 1| connects contact 52 to terminal 12; wire 13 connects Wire 5| to terminal 14.

Adjustable sighting bands 15 and 16 are adapted to be tightened in correct position by means of screws 11 and 18, which travel in slots 19 and 88.

Referring to Figure 2, motor 8| is connected by wires 82 and 83 to terminals 62 and 68. A cover 84 is adapted to be fastened over base Glass windows 85 and 86 allow vessel I4 and tube l5 to be inspected. Resetting button 45 projects through a slot in this cover. Terminals 6| and 64 are connected by wires 81 and 88 to the 110 or 220 volt house leads. Terminals 10 and 12 are connected by wires 89 and 90 to buzzer 9|. Terminals 14 and 58 are connected by wires 92 and 93 to thermostat 94.

The operation of the device will now be explained. It is well known in the art that the most efficient operating level for steam boiler water is just covering the crown sheet of the combustion chamber. However, the water is usually kept much higher than that due to the danger of uncovering the crown sheet as the water lowers when steam is produced or on account of small water leakages. As the present invention provides means for reducing or cutting off combustion, if the boiler water gets too low, the preferred way of installing the device is as follows: Base I is fastened to the boiler or contiguous thereto, at such a height that the center of tube l5, when in a vertical position, is level with the minimum height of water it is deemed safe to have in boiler 20 when the heating system is steam saturated. After the base is fastened and pipes l9 and 22 connected to hoses |8 and 2|, adjusting screws 4 and 5 are loosened and bracket 2 lowered or raised to bring the desired operating water level of boiler 20 accurately to the center of tube l5, when counterweight I3 is so adjusted that the tube is held vertical. Screw 96, which passes through bracket 2, is then tightented against the lower flange of base I, to prevent any slippage and screws 3 and 4 are tightened. The set-screw of counterweight I3 is then loosened and the weight is placed as far to the right as it will go, the water rising in tube |5 to the height of the water in boiler 20, due to the connection of pipe I9 to the bottom of the boiler and due to the venting of the air in tube l5 through pipe 22 above the water level of boiler 28. Sighting band 16 is normally adjusted so that its upper edge is just equal to the correct water level when tube I5 is vertical.

The contacts of thermostat 94 are then closed and a circuit is closed over the following path: Thermostat 94, wire 93, terminal 58, wire 51, solenoid 55, wire 54, secondary of transformer 53, wires 56 and 58, contact spring 24, contacts 26 and 21, contact 25, wires 5| and 13, terminal 14, wire 92, completing the circuit through thermostat 94. Solenoid 55 attracts its plunger, which tilts the contact end of mercury switch 42 downward. This establishes a circuit over the following pathz Mercury switch 42, wire 61, terminal 68, wire 83, motor 8|, wire 82, terminal 62, wire 60, terminal 6 wire 81 to the source of electricity, wire 88, terminal 64, wire 66, completing the circuit through mercury switch 42. This causes motor 8| to operate blower fan 95 to which it is connected. As blower fan 95 forces air into the combustion chamber of boiler 28, the consequent increase in combustion chamber temperature causes the boiler water to produce steam and this causes the boiler water to slowly lower, as the steam is disseminated through the heating system by way of pipe 96. To counteract this effect water is allowed to enter boiler 20 from house main 91, by opening valve 98, so that the starting water level in tube I5 is strictly maintained level with sighting band 16.

This process continues until steam radiator 99, which would usually be the radiator at a point farthest from the boiler, has had all the air expelled from it through air valve I00 and is consequently steam saturated. This can readily be determined by removing air valve I00 and noting when live steam, free from air mixture, is visible in the air valve opening. As in some installations a radiator nearer the boiler may be slower in reaching its steam saturation point, it is advisable to check all such radiators in the heating system. The water level in tube 15 is then brought exactly up to band 16 and valve 98 is closed. The contacts of thermostat 94 are then opened, solenoid 55 releases its plunger, mercury switch 42 resumes its normal position tilted backward and the circuit is opened through motor 8|. The blower fan stops, combustion is diminished, the boiler Water stops producing steam and the steam disseminated throughout the heating system condenses and runs back to the boiler through return pipe |0|. When the entire system has cooled ofi and all the water is back in the boiler, sighting band 16 is adjusted so that its upper edge is just equal to the water level at that time.

counterweight I3 is then adjusted so that tube I5 is balanced by vessel 4 and is held vertical with the water at the level mentioned. At the same time that the water was lowering in tube to the pressure developed. This pressure is indi-' cated on scale markings I02 on vessel I4. Normally, when counterweight I3 is properly adjusted, the weight of this water in vessel I4 assists in the tilting of cradle 6, but at present no such effect is produced.

After counterweight I3 has been adjusted, the contacts of thermostat 94 are again closed and the'heating system saturated with steam, which will be shown now by the water level in tube I5 lowering down to sighting band I6. This'lowering of the water lessens the weight on the right side of pivots I and 8 and the rising of the water in vessel I4, due to the steam pressure developed, has increased the weight on the left side and cradle 6 is unbalanced and tilts downward on the left and upwards onthe right, as shown by dot and dash lines I03. Adjusting screw 3| is now adjusted so that it forces insulating block 35 of circuit opener 33 against contact spring 24 sufliciently to open contacts 26 and 21, the long point of insulating block 23 assisting in the break. This at once opens the traced circuit through solenoid and the blower fan 95 is at once stopped.

' As soon as the steam in the heating system begins to condense and return to the boiler in the form of water, the lowering steam pressure in vessel I4, which is concurrent with the steam condensation, allows the air compressed in the upper part of vessel I4 to force out the water therein. This increases the weight on the right side of pivots I and 8 and decreases the weight on the left side and causes cradle 6 to partly resume its normal position, even though the water level in tube I5 may still be in the vicinity of sighting band I6. Adjusting screw 30 is then so manipulated that it forces insulating block 35 sufficiently to the right so that contact spring 24 reengages contact spring 25. Bracket 29 is wide enough so that circuit opener 33 can be given sufficient play sidewise to cause contact springs 24 and 25 to engage each other only when all the water has come back to the boiler, when the steam pressure has been lowered to nothing, when the steam pressure has fallen to any desired point, when a part only of the water has returned to the boiler, or by any combination of I these factors.

entered the heating system, will be automaticallyprovided; as the more air that has entered, the more water must have returned to the boiler and consequently the higher will be the steam pressure allowed to expel the air, as this pressure is increased by an increase in the amount of water in tube I5.

If at any time after first starting, when the water in tube I5 is in the vicinity of sightingband 15, very quick steaming produces a high enough pressure to make it advisable to shut ofi combustion, then the additional weight in vessel I4 overbalances whatever weight there may be in tube I5 and cradle 6 tilts to the left and the solenoid circuit is opened.

Assuming that it takes water in vessel I4 up to the five pound scale marking, to tilt cradle 6 when the water in tube I 5 is level with sighting band I5 and one-half pound when the water is' level with sighting band I6: then when starting with a cold heating system, five pounds will be the maximum allowable steam pressure at the start, which will be progressively lowered to the one-half pound point as steam saturation of the heating system is approached. The rapidity of this lowering of the water will depend on inside and outside temperature, which governs the rapidity of steam condensation in the heating system. On a cold day, the condensate will return to the boiler faster than on a warm day and consequently the allowable steam pressure will be greater on the cold day as the water level in tube I5 will drop slower. This is at it should be as the heating system will then reach its saturation point faster.

When adjusted, as described, and once the air is expelled from the heating system and until thermostat 94 is satisfied, cradle 6 will be tilted and the solenoid circuit opened and closed so as to just maintain the heating system steam saturated, the actual steam pressure being only that necessary to overcome pipe and radiator friction'and produce a radiator pressure just above atmospheric, thereby preventing ingress of air through the air valves.

. If for any reason it is desired to increase the restoration steam. pressure, this can be done by moving counterweight I3 to the right or by lowering bracket 2. In either case it will then take more water in vessel I4 to tilt cradle 6, and consequently this will entail a higher steam pressure.

As well as operating as a steam saturation control, a low water cut-off for the steam boiler is also provided. Should the water in boiler 20 lower to a certain point below sighting band I6, which can be to the crown sheet, as shown by dotted line IIII in Figure 2; the weight of tube I5 is reduced more than it is when steam saturation takes place. This unbalances cradle 6, without any raising of water in vessel I4, and it tilts, opening the solenoid circuit as described.

A high water cut-ofi is also provided, as should the water in tube I5 rise to a certain point above the level of sighting band 15, then the extra weight added to the tube I5 overcomes the bal ancing effect of counterweight I3 and cradle 6 tilts downward on the right of pivots I and 8 and assumes a position approximately as shown by dotted lines I05. Insulating block 35 of circuit opener 33 is forced against contact spring 25 and it is separated from spring 24, which opens the solenoid circuit.

Just as vessel I4, with scale markings I02, serves as a steam pressure gauge, so tube I5 alsov serves as a water level gauge, making these two common adjuncts to every steam boiler unnecessary, when my steam saturation control is used.

Optional with the device is an alarm whichproduces a signal whenever the solenoid circuit is opened by either high or low water, but not when opened by the described steam saturation of the heating system. The two terminals of the high resistance heating coil 46 are connected to contact springs 24 and 25 by wires 50 and 5I..

This constitutes a short-circuit for heating coil 45 except when springs 24 and 25 are disengaged. Due to the high resistance of coil 45, solenoid 55 does not receive sufiicient current to maintain its plunger attracted, but coil 46 does receive sufficient current to generate heat, whenever this short-circuit is removed. This heat is sufficient to warp bimetallic strip 41 upwards and the contact on its free end engages contact 52 after a definite time interval, Which can be varied by the adjustment of contact 52. This time interval is made slightly longer than the maximum time it takes cradle B to resume its normal position after steam saturation of the heating system. Hence, whenever contacts 26 and 21 remain open for a longer period than that rep resented by steam saturation, which will be caused by either high or low water, a circuit is closed over the following path: Buzzer 9|, wire 89, terminal I0, wire 59, secondary of transformer 53, wire 56, bracket 48, strip l! and contact on end thereof, contact 52, wire II, terminal I2, wire 90, completing the circuit through buzzer 9! and sounding an audible signal. A signal light or any other signal, can, of course, be substituted for the buzzer.

A main line circuit breaker is also optional with the device and is of particular use when the boiler combustion means comprises a more complex lay-out than that shown in the drawings. The description hereinbefore given has been limited to the opening and closing of the circuit through solenoid 55, which will usually be a lowvoltage circuit. When so desired, an additional safeguardagainst too high steam pressure and high or low water is provided, which becomes operative only after a predetermined additional rise in steam pressure or rise or fall of boiler water, than that required to open contacts 25 and 21. Prongs 36 and 3'! of circuit opener 33 are so adjusted that they do not force pin 38 to the left or right sufficiently to cause the top of trip 39 to clear the bottom of mercury switch holder 4|, until the desired additional tilt has been given to cradle 6 than is required to open contacts 26 and 21. However, when trip 39 does clear the bottom of holder 4|, either to the right or left, holder 4| falls downward on pivots 43 and. tilts mercury switch 42 backward, opening its contacts and the circuit through motor 8|, even though solenoid 55 should have its plunger attracted. The falling of holder 4| backward, moves extension 44 upward, forcing the free end of bimetallic strip 41 upward and engaging its contact with contact 52; hence, the alarm is sounded without waiting for the described time interval to elapse.

, Whenever holder 4| falls, trip 39 cannot resume its normal, vertical position and circuit opener 33 cannot close contacts 26 and 2'! until resetting button 45 has been manually depressed, thereby releasing trip 39. Hence, the solenoid circuit is held open at contacts 26 and 21, regardless of whether a normal steam or water condition is later on produced or not. Neither can holder 4| be reset on trip 39 until the normal balance of cradle 6 has been brought about by the reduction of the higher steam pressure or the restoration of the normal water level in tube I 5 by opening valve 98 or draining off excess water through valve I06, as until this balance is restored, the

top of trip 39 will not return to its normal position under the rear end of holder 4|.

This secondary safety cut-off is of great advantage particularly in the larger boiler installations, where a serious leak might quickly empty the boiler or where water injectors are used, which at times flood the boiler. It is also of particular advantage where boiler controls are used comprising various instrumentalities, some of which may not function quickly enough, in case of an emergency, as it furnishes a means of instantly cutting off the main current source of such instrumentalities.

In many boiler installations the return water comes back so slowly to the boiler that the water often gets temporarily too low for safe operation. This condition is provided for by the double low and high water cut-off described, as the combustion in boiler 20 is reduced by this temporarily low water and increased again when the water level becomes normal; but in case of a leak or other serious water loss, combustion is cut off until manual attention has been given to the control.

Whenever the water in tube I5 is higher or lower than sighting bands I5 or I5, but not high or low enough to cause contacts 26 and 21 to open, then more or less steam pressure will be required to open them than normally, as there will be more or less weight on the right side of pivots I and 8. This is as it should be, as the higher the water in any boiler, the less space for steam isavailable and consequently a higher pressure will be required and steam will be produced slower; the lower the water, the more space for steam is available, which will be produced faster and consequently, the less pressure will be required. Sighting bands I5 and I5 furnish con venient means for checking the proper water level in boiler 20. Band I5 is used if the heating system is cold and band I5 if it is steam saturated.

By loosening the set screws of clamp 9, pipe I can be shifted to the right or left, thereby increasing or decreasing the balancing effect of counterweight I3.

If the utilization of vessel I4 and tube I as steam and water level gauges is not desired, they may be made of a substance other than glass. In such a case the initial adjustment of tube I5 is made by bringing the water in the boiler to the desired point when steam saturation is obtained in the heating system and then merely balancing tube I5 in a vertical position, by means of counterweight I3, when the system is cold.

While I have shown a thermostat 9i as governing the device, a manually operated switch, or other circuit closing device may be substituted therefor.

The plugged openings at the bottoms of fittings I2 and II, are to facilitate cleaning of vessel I4 and tube I5.

While in the drawings, I have selected for disclosure a one pipe steam heating system, as that is the most common form, it will be understood that my device is equally applicable to a two pipe or a vacuum system, as it is also to any vessel containing any liquid whose level and internal pressure varies.

I claim:

1. A device of the character described comprising a boiler, a pivoted member, a tube supported by one end of said member, a closed vessel supported by the other end of said member, means connecting said vessel and the lower end of said tube to the lower portion of said boiler and connecting the upper end of said tube to the upper portion of said boiler, and means controlled by said pivoted member for regulating the supply of heat to said boiler.

of said boiler, means supporting said vessels for oppositely directed vertical movement in response to variations in liquid contents thereof, and means responsive to movement of said supporting means for controlling the supply of heat to said boiler. 1

3. A device of the character described comprising a boiler, a closed vessel connected to the lower'portion of said boiler, a second closed vessel connected at its lower end to the lower por tion of said boiler and at its upper end to the upper portion of said boiler, means supporting said vessels for oppositely directed vertical movement in response to variations in liquid contents thereof, means for regulating the supply of heat to said boiler, a switch controlling said regulating means and operated by limited movement of said vessels, a second means for opening said switch upon greater movement of said vessels, and means for locking said switch in open position after being opened by said second means.

4. A device of the character described comprising a boiler, a pivoted member, a tube supported by one end of said member, a closed vessel supported by the other end of said member, means connecting said vessel and the lower end of said tube to the lower portion of said boiler and connecting the upper end of said tube to the upper portion of said boiler, electrical means including a switch for controlling the supply of heat to said boiler, means normally holding said switch in open position, and electrical means responsive to movement of said member for closing and releasing said switch.

5. A device of the character described comprising a boiler, a closed vessel directly connected at its lower end to the lower portion of said boiler; a second closed vessel directly connected at its lower end to the lower portion of said'boiler and at its upper end to the upper portion of said boiler, means supporting said vessels for oppositely directed vertical movement in response to variations in liquid contents thereof, electrical means including a switch for controlling the supply of heat to said boiler, means normally holding said switch in open position, and electrical means responsive to movement of said supporting means for closing and releasing said switch.

6. A device of the character described comprising a boiler, a pivoted member, a tube supported by one end of said member, a closed vessel supported by the other end ofsaid member, means connecting said vessel and the lower end ofsaid tube to the lower portion of said boiler and connecting the upper end of said tube to the upper portion of said boiler, means for regulating the supply of heat to said boiler, a switch controlling said regulating means and operated by limited movement of said pivoted member, a second means for opening said switch upon greater movement of said pivoted member, and means for locking said switch in open position after being opened by said second means.

7. A device of the character described comprising a boiler, a closed vessel connected to the lower portion of said boiler, a second closed vessel connected at its lower end to the lower portion of said boiler and at its upper end to the upper portion of said boiler, means supporting said and releasing said switch.

vessels for oppositely directed vertical movement in response to variations in liquid contents thereof, electrical means including a normally open switch for controlling the supply or heat to said boiler, means responsive to limitedmovement of said vessels for closing and releasing said switch, and means responsive to additional movement of said vessels to render said lastnamed means inoperative and maintain said switch in open position. a

. 8. A device of the character described compris-v ing a boiler, a pivoted member, a tube supported by one end of said member, aclosed Vessel supported by the other end of said member, means connecting said vessel and the lower end of said tube to the lower portion oisaid boiler and connecting the upper end of said tube to the upper portion of said boiler, electrical means including a normally open switch for controlling the supply of heat to said boiler, means responsive to limited movement of said pivoted member for closing and releasing said switch, and means responsive to additional movement of said member to render said last-named means inoperative and maintain said switch in open position.

9. A device of the character described comprising a boiler, a pivoted member, a tube supported by one end of said member, means-connecting said vessel and the lower end of said tube to the lower portion of said boiler andconnecting the upper end of said tube to the upper portion of said boiler, electrical means including a switch for controlling the supply of heat to said boiler, means normally holding said switch-in open position, electrical means responsive to limited movement of said member for closing and releasing said switch, and means responsive to additional movement of said pivoted member to render said last-named means inoperative and maintain said switch in open position.

10. A device of the character described comprising a boiler, a closed vessel connected to the lower portion of said boiler, a second closed vessel connected at its lower end to the lower portion of said boiler and at its upper end to the upper portion of said boiler, means supporting said vessel and tube for oppositely directed vertical movement in response to variations in liquid contents thereof, electrical means including a switch for controlling the supply of heat to said boiler, means normally holding said switch; in open position, electrical means responsive to limited movement of said vessels for closing andreleasing said switch, and means responsive to additional movement of said vessels to render said last-named means inoperative and maintain said switch in open position.

11. A device according to claim 4, characterized by a thermostat responsive to air tempera ture controlling the electrical means for closing 12. A device according to claim 5 characterized by a thermostat responsive to air temperature controlling the electrical means for closing and releasing said switch.

13. A device according to claim 9 characterized by a thermostat responsive to air temperature controlling the electrical means for closing and releasing said switch.

14. A device according to claim 10, characterized by a thermostat responsive to air temperature controlling the electrical means for closing and releasing said switch.

15. A device of the character described comlower portion of said boiler, a substantially vertical tube connected at its lower end to the lower portion of said boiler and at its upper end to the upper portion of said boiler, means supporting said vessel and tube for oppositely directed vertical movement in response to variation in the liquid contents thereof, electrical means including a switch for controlling the supply of heat to said boiler, resilient means normally holding said switch in open position, electro-magnetic means for moving said switch into closed position, a pair of contacts in series with said electromagnetic means normally biased into engagement, and means responsive to movement of said vessel and tube for effecting relative movement of said contacts.

16. A device of the character described comprising a boiler, a closed vessel connected to the lower portion of said boiler, a second closed vessel connected at its lower end to the lower portion of said boiler and at its upper end to the upper portion of said boiler, means supporting said vessels for oppositely directed vertical movement in response to variation in the liquid contents thereof, electrical means including a switch for controlling the supply of heat to said boiler, resilient means normally holding said switch in open position, electro-magnetic means for moving said switch into closed position, a pair of contacts in series with said electro-magnetic means normally biased into engagement, and means responsive to limited movement of said vessels for efiecting relative movement of said contacts, and a member supporting said switch and movable in response to additional movement of said vessel and tube to release said switch to open position.

1'7. A device according to the character described in claim 15 characterized by a pivoted 1 member supporting said vessels at opposite ends thereof.

18. A device according to the character described in claim 16 characterized by a pivoted member supporting said vessel at one end and said tube at the other end.

19. A device of the character described comprising a boiler, a closed vessel connected to the lower portion of said boiler, a second closed vessel connected at its lower end to the lower portion of said boiler and at its upper end to the upper portion of said boiler, means supporting said vessel and tube for oppositely directed vertical movement in response to variations in the liquid contents thereof, means for regulating the supply of heat to said boiler including a mercury switch, an unbalanced pivoted member, a stop normally holding said pivoted member in said horizontal position, a lever pivoted to said member and supporting said mercury switch, resilient means normally holding said lever in switch-open position, electro-magnetic means responsive to limited movement of said vessels for moving said lever into switch-closed position, and means responsive to additional movement of said vessels for disengaging said stop from said pivoted member thereby resulting in movement of said pivoted member and lever into the switch-open position.

20. A device of the character described comprising a boiler, a closed vessel connected to the lower portion of said boiler, a second closed vessel connected at its lower end to the lower portion of said boiler and at its upper end to the upper portion of said boiler, means supporting said vessel and tube for oppositely directed vertical movement in response to variations in the liquid contents thereof, means for regulating the supply of heat to said boiler including a mercury switch, an unbalanced pivoted member, a stop normally holding said pivoted member in said horizontal position, a lever pivoted to said member and supporting said mercury switch, resilient means normally holding said lever in switch-open position, electro-magnetic means for moving said lever into switch-closed position, contacts in series with said electro-magnetic means for controlling energization thereof, means responsive to limited movement of said vessels for efi'ecting movement of said contacts into and out of engagement, and means responsive to additional movement of said vessels for disengaging said stop from said pivoted member thereby resulting in movement of said pivoted member and stop into switch-open position.

21. A device of the character described comprising a boiler, a pivoted member movable between two positions, a tube supported by one end of said member, a closed vessel supported by the other end of said member, means connecting said vessel and the lower end of said tube to the lower portion of said boiler and connecting the upper end of said tube to the upper portion of said boiler, heat supply means for said boiler, and means effective upon movement of said member into either of said two positions to render said heat supply means inoperative.

22. A device of the character described comprising a closed vessel directly connected at its lower end to the lower portion of said boiler, a second closed vessel directly connected at its lower end to the lower portion of said boiler and at its upper end to the upper portion of said boiler, means movable between two positions and supporting said vessels for oppositely directed vertical movement inv response to variation in the liquid contents thereof, heat supply means for said boiler, and means effective upon movement of said memberinto either of said two positions to render said heat supply means inoperative.

HUBERT S. TURNER. 

